As Alexander pointed out, you should usually be connecting to the last active connection. Is that not happening for you?
I'm not sure but I can see how things would be less than perfect if you alternate between two good connections. Let's say three connections "free-but-slow", "home" and "work". I cannot test now but I could imagine that when I alternate between "home" and "work" nm may drop back to alphabetical preference and try to connect to "free-but-slow" first. Is that what you are describing?
As Alexander pointed out, you should usually be connecting to the last active connection. Is that not happening for you?
I'm not sure but I can see how things would be less than perfect if you alternate between two good connections. Let's say three connections "free-but-slow", "home" and "work". I cannot test now but I could imagine that when I alternate between "home" and "work" nm may drop back to alphabetical preference and try to connect to "free-but-slow" first. Is that what you are describing?